Mr Kim's visit, during which he is being accompanied by several leading North Korean officials, is his fourth to China in less than a year.

Tuesday is also reportedly Mr Kim's 35th birthday, though his date of birth has never been confirmed by Pyongyang.

China is an important diplomatic ally for North Korea, and one of its main sources of trade and aid.

"[Mr] Kim is eager to remind the Trump administration that he does have diplomatic and economic options besides what Washington and Seoul can offer," Harry J Kazianis, Director of Defense Studies at the Centre for the National Interest told Reuters.

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Image caption Mr Kim's first visit to China came in March last year

Mr Kim, unusually, did not meet Mr Xi for the first six years of his leadership of North Korea.

But last year, he visited China three times. None of the trips was announced in advance.

The BBC's Laura Bicker in Seoul says two of the trips, which took place ahead of the historic summits with the South Korean leader Moon Jae-in and Mr Trump, were seen by some as a chance to co-ordinate strategy.

The latest three-day visit, our correspondent says, is likely to fuel speculation that a second US-North Korean summit will take place soon.

Earlier this week, Mr Trump said a location for another meeting between the two would be announced in the not-too-distant-future.

In his annual New Year's speech last week, Mr Kim said he was committed to denuclearisation, but warned that he would change course if US sanctions remained.

Diplomatic progress between Mr Trump and Mr Kim has stalled since the Singapore summit. Both parties signed a pledge at the time to denuclearise the Korean peninsula, though it was never clear what this would entail.